WDIO31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04B (FENGAL) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 81.5E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 80 NM EAST-SOUTHEAST OF CHENNAI, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT
TROPICAL CYCLONE (TC) 04B (FENGAL) CONTINUES TO STRENGTHEN AS IT
LINGERS OFFSHORE OF CHENNAI, INDIA. THE LATEST MSI AND INFRARED
LOOPS SHOW A PERSISTENT CENTRAL DENSE OVERCAST (CDO) FEATURE, WITH
OVERSHOOTING TOPS NEAR THE CENTER OF THE CDO AND TRANSVERSE BANDING
FEATURES EXTENDING OUTWARD FROM THE CENTER TOWARDS THE EAST. THIS
WOULD SUGGEST THAT THE LOCALIZED SHEAR OVER TOP OF THE SYSTEM IS
LIKELY A BIT LOWER THAN WHAT THE LATEST CIMSS ANALYSIS WOULD
SUGGEST. HOWEVER, WARMER, LOWER-LEVEL CLOUDS CAN BE SEEN MOVING
RAPIDLY WESTWARD UNDER THE OUTFLOW LAYER, INDICATING MID-LEVEL
SHEAR IS STILL RATHER HIGH. THIS IS BORNE OUT BY NORTHWESTWARD
VORTEX TILT SEEN IN A PARTIAL 292040Z AMSR2 PASS. ANIMATED RADAR
DATA FROM INDIA SHOWS STRONG BANDING FEATURES ON THE WESTERN SIDE
OF THE LOW LEVEL CIRCULATION CENTER (LLCC), BUT THE RADAR STILL
CANNOT SEE THE EASTERN SIDE, SO AS OF YET IT CANNOT BE CALLED AN
EYE BUT IT CERTAINLY IS TRENDING THAT WAY. THE INITIAL POSITION IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PARTIAL RADAR
COVERAGE, EXTRAPOLATION OF THE AMSR2 PASS NOTED ABOVE AND A 292231Z
TROPICS-5 91.66GHZ IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AVERAGE OF THE AVAILABLE OBJECTIVE
AND SUBJECTIVE ESTIMATES NOTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 51 KTS AT 300000Z
   CIMSS AIDT: 39 KTS AT 292300Z
   CIMSS D-MINT: 48 KTS AT 300022Z
   CIMSS D-PRINT: 63 KTS AT 300030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: HIGH MID-LEVEL SHEAR. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 04B WILL CONTINUE TO
TRACK SLOWLY TOWARDS THE NORTHWEST FOR THE NEXT 24 HOURS, ALONG THE
WESTERN SIDE OF THE STEERING RIDGE.  THE GFS CONTINUES TO SHOW THE
SYSTEM REMAINING OFFSHORE DUE TO THE PRESENCE OF A BUILDING RIDGE
IN THE NORTH ARABIAN SEA. THE GFS HOWEVER IS THE ONLY GLOBAL MODEL
PREDICTING THIS TRACK EVOLUTION, WHILE THE REMAINDER OF THE
RELIABLE MODELS SHOW THE SYSTEM MOVING IN A STEADY NORTHWESTWARD
DIRECTION FOR THE NEXT DAY. THE SYSTEM IS FORECAST TO MAKE LANDFALL
IN THE VICINITY OF CHENNAI AROUND TAU 24, THEN CONTINUE TO TRACK
FURTHER INLAND. IN TERMS OF INTENSITY, THE SYSTEM HAS OUTPERFORMED
UP TO THIS POINT, BUT THE PRESENCE OF MODERATE TO HIGH MID-LEVEL
SHEAR SHOULD START TO IMPACT THE SYSTEM IN THE NEAR-TERM. INTENSITY
IS EXPECTED TO REMAIN AT AROUND 50 KNOTS FOR THE NEXT 12 HOURS,
THEN BEGIN TO DROP DUE TO INCREASING SHEAR. AFTER MAKING LANDFALL,
THE SYSTEM WILL QUICKLY WEAKEN AND DISSIPATE OVER LAND WEST OF
CHENNAI. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN POOR AGREEMENT
ON THE TRACK FORECAST. THE GFS AS MENTIONED ABOVE, TRACKS WEST FOR
ABOUT 12 HOURS THEN TURNS BACK EAST, STALLS FOR 24 HOURS THEN
EVENTUALLY MOVES THE SYSTEM BACK INLAND AROUND TAU 72. THE GEFS
ENSEMBLE MEAN TRACKS THE SYSTEM DUE WEST WHILE THE ECMWF TRACKS THE
SYSTEM STRAIGHT SOUTHWESTWARD FROM THE BEGINNING OF THE FORECAST.
THE REMAINDER OF THE CONSENSUS MEMBERS INDICATE A NORTHWESTWARD
TRACK ROUGHLY IN LINE WITH THE JTWC FORECAST, WHICH STICKS CLOSE TO
THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN
POOR AGREEMENT AS WELL, WITH THE COAMPS-TC AND HWRF INDICATING THAT
THE SYSTEM WILL MAINTAIN ITS CURRENT INTENSITY FOR THE NEXT 12
HOURS, THEN WEAKEN SLIGHTLY UP TO LANDFALL, BEFORE DISSIPATING
INLAND. THE GFS AND HAFS-A, WHICH KEEP THE SYSTEM OVER WATER, HOLD
THE SYSTEM INTENSITY HIGHER FOR LONGER. THE JTWC FORECAST LIES
CLOSE TO THE HWRF AND COAMPS-TC WITH MEDIUM CONFIDENCE.  

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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